Carburetor for internal combustion engines



1941- c. cs. PICKERING CARBURETOR FOR INTERNAL CbMBUSTION ENGINES Filed March 15, 1939 5 Sheets-Sheet 1 Inventor Nov. 1 1941.

c. G. PICKERING CARBURETOR FOR INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 2 Filed March 15, 1959 18, 1 c. G. PICKERING CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed March 15, 1939 3 Sheets-Sheet 3 YEN T e c/meLEs q, P/cKsei/vq Patented Nov. 18, 1941 CARBURETOR FOR INTERNAL COMBUSTION I ENGINES Charles Greenbank Pickering, Maidstone, England, assignor, by direct and mesne assignments, to Pickering Carburetters Limited, London, England, a body corporate of England Application March 15, 1939, Serial No. 262,008 In Great Britain July 22, 1937 1 Claim.

This invention relates to carburetors for internal combustion engines more especially for motor vehicles and has for its main object to pro vide an improved method of carburation and an improved construction of carburetor ensuring an appropriate supply of combustible mixture under all service conditions.

Further and favourable objects will appear from the following description.

Broadly stated, a method of carburation for internal combustion engines in accordance with the invention consists in heating a mixture of fuel and primary air, admitting secondary air for admixture therewith through a suction controlled aperture, regulating the heating mixture of fuel and primary air to give a relatively richer mixture as the throttle is opened by positively varying the effect of the primary air on the nozzle, and simultaneously regulating the maximum aperture for the inlet of secondary air in consonance with the throttle opening.

The improved carburetor includes a heated mixing chamber for fuel and primary air, a suction operated valve passing cold secondary air into admixture therewith and an over-riding control for said secondary air valve preventing its opening except when the throttle is opened.

Preferably the mixing chamber is an exhaust heated cylindrical receptacle, having unions by which it may be interposed in the exhaust system of the engine, the mixture passing through a substantially volute passage within such receptacle on its way to the induction manifold, the passage for the mixture being thus of divergent or increasing cross-section to accommodate the increasing volume of the gases as they undergo expansion in consequence of the heat obtained from the exhaust system. Alternatively, the mixing chamber may be heated by other convenient means.

Conveniently the area of the induction pipe at or in the vicinity of the point of entry of the heated mixture from the mixing chamber is variable in consonance with the engine requirements to vary the volume of cold air admitted as required and, to this end, a valve is positioned in the induction pipe at this point and normally closes the half thereof remote from the mixture inlet, a spring opposing the opening of this valve under the influence of the suction and the aforementioned over-riding control being furnished so that the valve is positively prevented from opening except when the accelerator is depressed.

A variable jet or nozzle may be employed for passing to the heated mixing chamber, although preferably for the positive regulation of the heated mixture there is employed a jet having a semi-circular sleeve normally masking such jet and being rotated when the accelerator is de pressed and the throttle opened proportionately to increase the effect of the passing air on the jet, whereby a richer mixture is obtained as conditions require it and conversely, for instance, when decelerating, the mixture is automatically weakened.

The invention will be further described with reference to the accompanying explanatory drawings which illustrate one embodiment thereof, and in which- Fig. 1 is an elevation and Fig. 2 a plan of a down draught carburetor assembly, Figs. 3 and 4 being detail views of the preferred form of variable main jet and Fig. 5 a diagrammatic showing of the system adopted for controlling the admixture of fuel and secondary air.

Fig. 6 is a central vertical section of the carburetor shown in Figs. 1 and 2.

Referring now to the drawings, I generally designates the inlet pipe and mixing tube of the carburetor which is formed integral with a float chamber 2 of any conventional or appropriate form and has a flange 3 for connection to the induction manifold of an internal combustion engine. The inlet pipe I is also furnished with a second flange 4 to which is attached the heated mixing chamber 5 by bolts 6 with an appropriate heat insulating packing l.

The mixing chamber 5 is shown as an inverted cup shaped casting, the open mouth whereof is furnished with a coverplate 8 having unions 9 and ID for connection to pipes II and I2 respectively, via which the interior of the mixing chamber 5 may be put into communication with the exhaust system of the engine.

Within the exhaust heated mixing chamber 5 is the aforementioned volute pipe or duct l3 for the fuel-air mixture, this duct connecting the primary air inlet I4 through the heater 5 and the flange 4 to the interior of the main inlet or mixing tube l on the carburetor side of the throttle l5, shown, of conventional form.

The volute passage is shown of divergent section in both the horizontal and the vertical plane and is thus of increasing cross-section to accommodate the increasing volume of the gases as they undergo expansion in consequence of the heat obtained from the exhaust system and has smooth internal walls free from excrescences or admitting fuel into mixture with the primary air 55 obstructions which might produce eddies or otherwise impede the passage or volatilisation of the mixture.

The main inlet pipe I may be furnished with a choke tube although, in the embodiment illustrated, one half thereof is blanked in the vicinity of the point of entry of the heated :mixturefrom the mixing chamber by a filling piece l6 (See Fig. 6) secured by a screw H, the effective aperture of the remaining half being regulated by a flap or half butterfly valve I to vary the volume of cold air admitted, such valve normally closing the half of the inlet pipe I remote from the mixture inlet. The flap valve I8 issuction operated an over-riding control lever or camfollower l9, hereafter more fully described, being provided for such valve to prevent its opening except when the throttle is opened. I

indicates a conventional pilot jet. *The preferred embodiment illustrated employs a variable main jet or nozzle generally designated 22 and located near the mouth of the primary air inlet 14 as more clearly illustrated j in Figs. 3 andl. Around the jet 22 'is disposed at part circular sleeve 23 which normally masks the jet, being urged to this position by a spring 24, such sleeve being rotated when the accelerator is depressed and'the throttle opened proportionately to increase the effect of the'suction through the primary air inlets M on the jet 22 whereby a richer mixture is obtained as conditions require it and, conversely, for instance, when decelerating, the mixture is automatically weakened. i

For operating the semi-circular sleeve 23 it is furnished with acranked arm 25 with which cooperates an abutment 26 associated with the throttle lever 21 the abutment 26 being adjustably connected to such throttle lever to permit any predetermined or desired setting as between the throttle and the jet'to be accomplished.

"28 indicates the spindle of the throttle i5 and on the side remote from the lever 2'! such spindle is shownfurnished "with a cam 29 'upon which bears a roller 30 carried by the end of the aforementioned control arm IQ for the secondary air valve I8. A spring (not shown) may urge the lever 19 to close the valve'lfi, the strength of the spring being insufiicient fully to counteract the effect of the suction on the valve it when the throttle I5 is opened under certain conditions.

In use, a pilot jet 20, and main jet or nozzle 22, appropriate to the engine with which the carburetor is associated having been selected, correct setting isestablished "between the throttle lever Y21' and the adjustable main jet 22 on the one hand and the secondary air butterfly 18 on the other. When the engine is idling mixture is fed by the pilot jet 20 and withit may be some primary heated air through the volute duct l3, the semi-circular sleeve 23 being in its masking position.

On the throttle being partly opened the sleeve 23 for the main jet 22 "remains in it's adjusted butterfly l8 so that if theen'gine speed is sufficient to produce the necessary suction this latter valve is opened and cold, secondary air admitted as required. I

It will be appreciated that the arrangement provides the most advantageous carburation in that only so much primary air as is necessaryfor the efiective volatilisation of the fuel need be passed through the inlet I4 and volute heated mixing duct 13, the remainder or secondary air being 'admittedcold and therefore dense past the butterfly I 8 whereby an optimum charge is achieved. Moreover since, at low engine speeds.

the suction will normally be insuflicient to retain the secondary butterfly valve l8 open on the throttle being opened, a rich charge likely to-give the best acceleration is admitted under these conditions; 2| is an adjusting screw which serves as 'an adjustable stop for the throttle lever 21.

It will be understood that the particular embodiment of downdraught carburetor is illustrated only by way of example and that the invention may equally well be applied to uptake carburetors and withor without an-air cleaner of known form; and further that a needle type variable main jet may beemployed.

For starting purposes a conventional choke may be provided and/or a starting carburetor-of the usual known form so devised as to pass a rich combustible mixture to the engine side of the main throttle, the latter arrangement being preferred.

By the present invention an improved construction of carburetor is obtained giving enhanced power consistent with economy under running conditions.

WhatI claim is:

LA carburetor for internal combustion engines, including a throttle, a heated mixin-gchamber for fuel and primary air and a fuel noz zle, positive means for regulating the effect of primary air on the nozzle as the throttle is opened to in crease the proportion of fuel to'prirnary air in the mixture passing to the heated mixing chamber, a suction operated valve passing secondary air into admixture with such heated fueland air'mixture, and means operated by saidthrottle and associated with said secondary air'valve for variably limiting the extent of the opening ]of said valve according to the opening 'of' the throttle; said fuel nozzle regulating means comprising a fuel jet "and a part circular sleeve normally masking said jet but rotated when the throttle is open to expose the jet to the full suction of the primary air passing to the mixing chamber.

CHARLES 'GREENBANK PIC'KERING. 

